The proposed SLP attribute API is beta. Download it from http://download.sourceforge.net/ssb/slp_attr.tar.gz
SSB now has docs. So add service commands to your hearts content.
Initial release of SSB, the SLP Service Browser. It shows the SLP-aware resources available on a network. It uses OpenSLP: http://www.openslp.org
Needs docs, and a heafty code cleanup and review.